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#19: Healthy, Safe & Engaging: Sound Loudness & Level Basics For Churches

Untangling the difference between loudness and level – it’s a distinction that might not be immediately clear, but it is important to understanding the bigger picture of a crucial issue.

For many churches, live music plays a pivotal role in the modern worship experience. This can often lead to contention between musicians, leadership, and members of the congregation about “how loud is too loud.” Some might want the mix to be louder, some might think it’s too loud, and others might feel it’s fine the way it is. This highlights the subjective nature of loudness perception – and if someone feels uncomfortable, who are we to tell them they’re wrong?

The key to untangling these situations lies in the difference between loudness and level. It’s a distinction that might not be immediately clear, but it is important. Loudness refers to our subjective perception, which is unique from person to person and from day to day. A complex stew of factors contributes to our loudness perception, including tonal balance, listener fatigue, intelligibility, distortion, even whether we like what we’re listening to. Thus, we can’t tell another person whether something is too loud for them, just as we can’t tell them whether they’re hungry.

By contrast, Sound Pressure Level (SPL), is an objective measure of the pressure variations in air caused by sound waves. It’s a physical quantity that we can measure, just like weight or temperature. An SPL meter doesn’t measure “how loud it is” – it measures level, which helps us answer objective questions, like whether levels present a risk of hearing damage, or violate health and safety regulations, building policies, or noise ordinances.

Danger Versus Discomfort

The distinction between loudness and level means that our ears can’t tell us whether levels are safe. It’s possible to be exposed to dangerous sound levels and still feel completely comfortable, or for a sound to be uncomfortably loud yet perfectly safe.

If someone complains that the music is “too loud,” further discussion can help determine their true concern is – would they simply prefer a less loud experience? Or are they worried about hearing loss?

Understanding Sound Exposure

Since sound exposure risk is determined by not only level, but also length of time, it’s not possible to declare a single decibel value “safe” or “unsafe.” Rather, we must consider how long people will be exposed to sound at that level.

A simple way to think about sound exposure is “how loud for how long.” In other words, sound exposure risk is determined both by level and length of exposure. This is commonly characterized as a dose, with a full dose (100 percent) representing the maximum amount of sound energy that a person should be exposed to over the course of a day or work shift. Higher sound levels will result in a full dose being reached in shorter amounts of time. For this reason, determinations of level limits should consider the duration of the services, especially for technicians or musicians who might be participating in several services a day.

Many musicians and sound techs are familiar with the legal regulations concerning sound exposure under OSHA (Occupational Safety and Health Administration); however, it’s often overlooked that OSHA’s limits don’t indicate what’s actually safe, rather they indicate the threshold of legal liability. In other words, OSHA indicates when levels are high enough to constitute a workplace hazard, and sound levels that fall “just under” OSHA’s limits still constitute a significant health and safety risk.

A better indicator of safe sound levels comes from NIOSH (National Institute for Occupational Safety and Health). NIOSH has recommended limits that are well rooted in audiological data concerning hearing loss (1).

The takeaway: If our question is whether levels are legal, we turn to OSHA. If our question is whether levels are safe, we look to NIOSH. Smaart SPL, the platform offered by Rational Acoustics, can measure both NIOSH and OSHA sound exposure directly as percent dose.

Figure 1: Both OSHA (Exposure O) and NOISH (Exposure N) dosimeter readings in Smaart – notice how NIOSH exposure is about to pass 75 percent dose while OSHA has not even hit 5 percent. This illustrates the difference between what is legal and what is safe.

Effective Metering

Since the rhythms and dynamics of live music fluctuate very rapidly with time, the traditional “Fast” and “Slow” ballistics found on most handheld sound level meters and apps don’t do a good job characterizing the trend in levels over time, making it difficult to make meaningful statements about the level of a verse, song, or set.

For this reason, the industry has standardized around a longer-term average called Equivalent Continuous Sound Level (Leq), which give more much-needed context about levels over time. Commonly, live music levels are evaluated as a 15-minute average (Leq 15). This allows the mix to retain dynamic loud and soft moments while keeping the long-term levels in check.

Multiple frequency weightings are in common use, however many SPL “speed limits” use A Weighting as it tends to correspond well with sound exposure models. For example, a church might institute a limit of “92 dB LAeq 15” as measured from mix position. C Weighting includes more low frequency energy than A Weighting, making it a better choice when measuring to characterize bass energy that might disturb neighbors.

Figure 2: The dynamic SPL Slow data in blue, while a 10-minute average (Leq 10) in orange more readily indicates level trends.

Three-Pronged Attack

Sound level metering is most effective as a “three-pronged attack.” First, reasonable, actionable and well-defined levels, limits and expectations should be established and communicated to all parties. Some churches post their sound level policies on their websites so anyone interested may learn about them.

Second, clear and accessible metering provides real time feedback to the console operators during the service, so they can adjust and react immediately to keep levels on target. Optionally, levels can be monitored remotely via a web browser if additional accountability is desired.

Third, the SPL log data is kept on record so it can be referenced afterwards to investigate any complains or issues. In this way, issues can be evaluated and dealt with in an objective, responsible manner that is fair to all parties, rather than hinging on disagreements over perception. In this way, a productive, informed discussion can move forward with the knowledge that levels are safe and in compliance with all policies.

The Right Tools

Although inexpensive handheld meters and smartphone apps may be entertaining and convenient, they don’t meet the levels of accuracy, performance or functionality required to be useful for evaluating sound level safety or compliance. It requires an audio interface, coupled with a sound level calibrator and a measurement microphone that can respond accurately to live music signals.

Alongside Smaart SPL software, this configuration allows the user to monitor sound levels in a variety of weightings and averages, record level violations, create time-stamped log data for posterity, view levels remotely from any network-connected device, and prepare PDF reports for review.

Accurate, detailed information about sound levels is a critical prerequisite to creating a healthy, safe and engaging worship environment for your congregation.